This invention relates to novel phosphite compounds which are useful as stabilizing agents for organic materials. Since organic materials which consist of natural macromolecules, synthetic macromolecules, fats and oils, lubricants, working oils or so on are subject to oxidation and decrease in utility, various antioxidants have been devised and have been added to these organic materials. It is known that stabilizers such as hindered phenols, organic sulfur compounds, organic phosphorus compounds and aromatic amines have stabilizing effects when used singly or in combination. The above-mentioned stabilizing agents have their respective merits and are useful. In particular, phosphite compounds of organic phosphorus compounds are widely used as antioxidants.
As concrete examples of phosphite compounds, there have been known the compounds which are described in the gazettes of Japanese Patent Application Examined Publication (Kokoku) No. 1641/1958 and Japanese Patent Application Unexamined Publication (Kokai) No. 4629/1984.
As concrete examples of attempt for stabilizing effects with the combined use of phosphite compounds and hindered phenol compounds, there have been such combined use in the gazette of Japanese Patent Application Examined Publication No. 12373/1962 in the specification of U.S. Pat. No. 3,558,554, in the gazette Japanese Patent Publication Application Unexamined Publication No. 109050/1976 and in the gazette of Japanese Patent Application Examination Publication No. 21822/1987.
However, the above-mentioned phosphite compounds hitherto known include various problems, and satisfactory phosphite compounds are thus far unknown.
Specifically, the above-mentioned known phosphite compounds have problems which include, among others, the problem that since the phosphite compounds are susceptible to hydrolysis and thermal decomposition, sufficient stabilizing effect cannot be realized and inconveniences such as corrosion and foul-smell are apt to occur. Phosphite compounds having sterically bulky structure in the neighborhood of the phosphite bond involve the problem that they are difficult to synthesize. For example, in the case where tris(2,4,6-trisubstituted phenyl)phosphites have a bulky group such as tert-butyl group as the substituents at the 2- and 6- positions, they are difficult to synthesize and are industrially less valuable.